drm/amdgpu: fix a memory leak in amdgpu_ras_feature_enable

This patch fixes a memory leak in the amdgpu_ras_feature_enable() function.
The leak occurs when the function sends a command to the firmware to enable
or disable a RAS feature for a GFX block. If the command fails, the kfree()
function is not called to free the info memory.

Fixes: 9f051d6f

 ("drm/amdgpu: Free ras cmd input buffer properly")
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Cong Liu <liucong2@kylinos.cn>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>